Reduction systems of the transmissions of the Background Art Copending Applications may include a respective ring gear that is axially moveable to selectively operate the same. Each ring gear (e.g., 380s in FIG. 9 of the '200 application, or 12 in FIG. 2 of the '503 application) may respectively support a radially-oriented cam follower. For example, the outer surface of the ring gear may be provided with a continuous, circumferential groove (17 in FIG. 2 of the '503 application) in which may be located a shifter wire 101 (see Background Art FIG. 1, also, e.g., 312s in FIG. 9 of the '200 application, or 18 in FIG. 2 of the '503 application), ends of which function as cam followers.
Shifter wire 101 may be described as being similar in appearance to the Greek letter omega (Ω). Shifter wire 101 may be slidable through the circumferential groove. And shifter wire 101 may have a circular body portion 102 and free ends (or, in other words, ears) 104 and 106 that extend in a radial direction and out of the circumferential groove.
Ears 104 and 106 of shifter wire 101 may constitute cam followers for the corresponding ring gear. The cam followers may be received in respective slots (e.g., 313t, 315 or 313s in FIG. 9 of the '200 application) of a corresponding shift collar (e.g., 310 in FIG. 9 of the '200 application) mounted on a housing (e.g., a gear housing such as 395 in FIG. 9 of the '200 application). Such slots are at least partially circumferential. If one were to trace such slots circumferentially, each may be described as zigzagging relative to the axial direction, where such zigzagging defines a cam profile.
Upon rotating shift collar, the slots may axially move ears (cam followers) 104 and 106 (and thus the corresponding ring gears) to the desired axial positions. Via such movement of the ring gear(s), a change in the gear ratio of the transmission can be achieved.
To change the gear ratio, transmission parts must disengage and re-engage when the corresponding shift collar is rotated by a user. Sometimes, splines (also referred to as lugs or teeth) on a ring gear do not align sufficiently to a feature with which the ring gear is to cooperate (e.g., the teeth of a gear), thus restraining if not preventing the splines from meshing adequately (if at all) with the teeth. As a consequence, the shift collar feels to a user as if it is jammed. In that circumstance, the act of making a shift (by rotating the shift collar) cannot be completed until the user at least briefly energizes (or, in other words, blips) the motor of the power driver (e.g., drill). Blipping the motor causes a slight rotation (a small angular displacement) of the armature shaft thereof and the gears connected thereto, which results in a change of alignment of the teeth with respect to the splines. Such a small angular displacement is typically sufficient to permit the splines and teeth to adequately align, thus permitting completion of the shift.
Such misalignment and the need to blip the motor is perceived by some users as a nuisance.